JPH063430B2 - Oxygen sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an oxygen sensor having a heater for heating an oxygen detecting element.

[0002]

2. Description of the Related Art Conventionally, in an oxygen sensor for detecting the oxygen concentration in the exhaust gas of various combustion equipment including an internal combustion engine,
Those using an oxygen sensing element made of a solid electrolyte such as zirconia are widely used. Further, some oxygen detecting elements have a heater for heating inside the oxygen sensor since the oxygen detecting ability is improved by maintaining the oxygen detecting element at a predetermined temperature.

An oxygen sensor having such a heater is
An oxygen sensing element made of zirconia or the like, which is closed at one end and formed in a tubular shape, and an inner electrode layer and an outer electrode layer made of platinum or the like formed on the inner and outer surfaces thereof, and electrically connected to the inner electrode layer. The internal electrode includes an output lead wire for taking out an output, a housing electrically connected to the external electrode layer for holding the oxygen detection element, and a heater for heating the oxygen detection element. Air layers,
The oxygen concentration in the exhaust gas is detected by bringing the external electrode layer into contact with the exhaust gas.

[0004]

By the way, since it is necessary to bring the internal electrode layer into contact with the outside air and to connect it to the lead wire for output extraction, there are various ways to connect the internal electrode layer and the lead wire for output extraction. There was a drawback. Further, it is necessary to dispose the heater inside the oxygen detecting element, that is, inside the internal electrode layer. Especially when a rod-shaped ceramic heater is used as the heater, there is a problem in the fixing method of the heater body. It was

For example, when connecting the internal electrode layer and the output lead wire, a female thread is engraved on the inner surface of the open end of the oxygen sensing element, and a tubular metal terminal is engraved with a male thread, or a coil shape. The internal electrode layer and the output extraction lead wire are electrically connected by screwing the terminal of (1) into the female screw portion and connecting the terminal to the output extraction lead wire. However, when using a tubular metal terminal engraved with a male screw part, there is a problem that a large tightening stress is applied to the female screw part and the oxygen detection element is damaged, while when using a coiled terminal Since the oxygen detecting element is not damaged because the tightening stress is not applied, it is not easy to screw the coil-shaped terminal into the female thread portion, which causes a problem that it takes time.

The heater is fixed with an adhesive or the like so as to heat the oxygen detecting element. In this case, the heater is heated with vibration of the adhesive or the like and changes with time. In particular, there is a problem in that the ceramic heater cannot be firmly fixed, and the oxygen detection element, especially its internal electrode layer and the heater itself are damaged.

Therefore, the present invention provides an internal electrode layer or oxygen sensor.
By using a metal terminal that has an elastic force that presses the inner circumference of the intelligent element from the inner side to the outer side in the radial direction and that can hold the heater, the oxygen sensing element is prevented from being damaged and the assembling work is facilitated. , Moreover heaters especially ceramic heaters
The purpose of the present invention is to provide an oxygen sensor that is firmly fixed without damaging the battery .

[0008]

To achieve the above object, a structure of an oxygen sensor according to claim 1 is a cylindrical oxygen detecting element having an electrode layer on the inner and outer surfaces and one end of which is closed, and the cylindrical oxygen detecting element.
A heater for being inserted into Jo to heat the oxygen sensing element, and electrically connected to the lead wire for the output take-out and the internal electrode layer of the oxygen sensing element inner surface, the oxygen sensor wherein the output Lead wire for extraction and the internal electrode layer
The metal terminal for electrically connecting the
In the tubular shape of the oxygen sensing element,
Due to the elastic force of the metal plate, the oxygen detection element is radially outside.
Connection part for pressing and fixing the internal electrode layer toward the side
And a grip portion for gripping the heater.
To collect.

Further , the structure of the oxygen sensor according to claim 2
Is a cylindrical oxygen sensing element with one end blocked, and
Inserted in the chamber to heat the oxygen sensing element.
In an oxygen sensor including a quartet, the ceramic
For fixing the heater to the oxygen detection element
Metal fittings are made by bending a metal plate into a tubular shape to detect the oxygen
In the tubular shape of the element, the elastic force of the metal plate
The inner peripheral surface of the oxygen sensing element is pressed radially outward to secure
A fixing part, and a holding part for holding the ceramic heater,
It is characterized by having.

[0010]

[Operation and effect of the invention] The oxygen sensor according to claim 1
Then, the metal terminal used for electrical connection between the internal electrode layer on the inner surface of the oxygen detection element and the output extraction lead wire is
It is made by bending a metal plate into a cylinder, and
The elastic force of the metal plate directs the oxygen detection element outward in the radial direction.
Oxygen test and the connection part that presses the inner electrode layer to set it.
It has a grip part for gripping the heater for heating the intelligent element.
It

Therefore, the internal electrode layer and the metal terminal are connected to each other.
Since it is electrically connected by the elastic force of, it is firmly connected without the need to engrave a screw part on the internal electrode layer,
The output from the internal electrode layer can be reliably taken out, the mounting work can be easily performed, and the oxygen detection element can be prevented from being damaged by the tightening stress.
In addition, the heater is connected to the oxygen detection element through the grip.
Since it is firmly fixed in the cylindrical shape and it is not necessary to use an adhesive or the like, it is possible to prevent the heater and the internal electrode layers from being damaged or damaged by the influence of heat and vibration.

Further, in the oxygen sensor according to claim 2,
The metal fixture for holding the ceramic heater in the holding part
Oxygen is generated by the elastic force of the fixing part that is formed by bending the metal plate into a tubular shape.
It can be settled firmly inside the tube of the sensing element in a stable state
It Therefore, it is possible to perform the assembling operation of the oxygen sensor formed by inserting the ceramic heater data into the cylindrical inner oxygen sensing element easily.

Moreover, the fixing portion is formed by bending the metal plate into a tubular shape.
The elastic force causes the inner peripheral surface of the oxygen sensing element to
Pressed to the outside and settled. Therefore, even if the oxygen sensor
If vibration or shock is applied to the oxygen sensor from outside the
Also, the fixed part plays a cushioning function and is transmitted to the ceramic heater.
Vibrations and shocks from the outside of the oxygen sensor
Prevents damage to the ceramic heater due to motion or shock.
You can

[0014]

【Example】

An embodiment of the present invention will be described below with reference to the drawings.
However, the present invention is limited to the examples described in detail below.
Instead, the person skilled in the art can think of it within the scope of the present invention.
Includes all possible implementations.

FIG. 1 is a partially cutaway front view (a) and left side view (b) of the oxygen sensor of this embodiment. In the figure, 1 is an oxygen sensing element made of a solid electrolyte such as zirconia formed in a cylindrical shape with one end closed, 2 is a platinum inner electrode layer deposited on the inner surface of the oxygen sensing element 1 by vapor deposition, 3 Is a platinum outer electrode layer deposited on the outer surface of the oxygen sensing element 1 similarly to the inner electrode layer 2, 4 is electrically connected to the inner electrode layer 2, and output extraction for extracting the output of the inner electrode layer 2 Lead wire 5 is electrically connected to the external electrode layer 3 and has a cylindrical housing for holding the oxygen detection element 1, and 6 is the inside of the oxygen detection element 1, that is, the internal electrode layer 2
Is a heater made of a rod-shaped ceramic for heating the oxygen detection element 1 disposed in the inner hole of the. Used here
The ceramic heater 6 is a raw wire formed in the shape of an elongated tube.
Around the luminal core, a predetermined shape of tungsten
Alumina raw sheet with a printing pattern printed on one side
Wrap it around and stick it tightly.
Guide to both ends of the buried pattern via
Form the printed surface of tungsten that will be the terminal surface for connection
After that, it is fired, and then the exposed surface of the tungsten
The outer diameter is nickel plated
About 2.5 mm, it was of also form tubular shape of length about 60 mm. A screw portion 5a for attaching to a combustion device is engraved on the outer periphery of the housing 5, and a gasket 7 is provided at a portion contacting the wall surface of the combustion device so that exhaust gas does not leak. Further, the housing 5 is formed with a caulking portion 5b, and by caulking the caulking portion 5b, the plate packing 8, the talc 9, the caulking ring 10 and the outer tubular collar provided on the inner circumference of the housing 5. Oxygen sensing element 1 via the portion 16a
Will be gripped by the housing 5. Reference numeral 11 denotes a protector for protecting the oxygen detection element 1 having a plurality of exhaust flow holes 11a formed therein so that the exhaust gas may come into contact with the external electrode layer 3, and is attached to the combustion device side tip portion 5c of the housing 5. Has been.

Next, 12 and 13 are heater lead wires for supplying power to the heater 6, which are heater terminals 14,
14 'is connected to the terminal surface of the heater 6 respectively.
There is. That is, one end of the heater terminals 14, 14 'is
Known for electrically connecting terminals and lead wires, respectively
Of the heater lead wires 12, 13 by crimping, which is the method of
The other ends of the heater terminals 14 and 14 'are connected to each other.
Each terminal is joined to the heater 6 by brazing
Has been done. Reference numeral 15 denotes a metal terminal for connecting the internal electrode layer 2 of the oxygen detection element 1 and the output extracting lead wire 4 and for holding the heater 6, which is a spring steel plate, here a deposit.
Hardened stainless steel strip for spring SUS6
31-CSP (JIS G4313) will be described later.
Round it so that it exhibits a radial resilience, like
The connection part 15a made and the same as the above-mentioned ceramic
Insert the kueater and grasp it elastically.
Of the heater grip 15b to be held and the output lead wire 4
It is connected to the core wire by crimping, which is a well-known joining technique.
Known crimping terminal parts that can be continued (Fig.
(Not shown), and the connecting portion 15a holds the heater.
The inner diameter of the oxygen sensing element was slightly enlarged while holding it.
Insert it by applying compressive force into the opening inlet and then open it.
The internal electrode layer 2 deposited on the inner surface of the opening by
The ceramic heater 6 is fixed in the pressure contact state.
It is held in place and electrically connected to the internal electrode layer 2.
Connected. The connecting portion 15a of the metal terminal 15 is
It also has a function as a fixing part in the invention according to claim 2.
ing. Although not shown, the core wire of the output lead wire 4 is connected to the crimping terminal portion of the metal terminal 15 by crimping, which is a known technical method for connecting a normal lead wire to the metal terminal. There is. Reference numeral 16 is an outer cylinder that extends from the crimped portion of the housing to protect the ceramic heater and the metal terminals, and 17 is a protective outer cylinder that is fixed by being fitted over the outer cylinder 16. Due to the protective outer cylinder 17, the lead wires 12, 13, 4 are respectively provided between the inwardly bent edge of the protective outer cylinder 17 and the similarly inwardly bent edge of the outer cylinder 16. The inserted sealing material 18 and the spacer 17 are held, and the connecting portion between the heater 6 and the lead wire and the connecting portion between the metal terminal and the lead wire are protected.

Further , a metal which is a main part according to the present invention
The shape of the terminal 15 will be described with reference to FIG. Metal terminal 15
As is apparent from the development view (b) in FIG. 2, the center is the connecting portion 15a and the notches 15c are formed on both sides thereof.
Two grips 15b are formed, and one grip 1 is further formed.
A known crimping terminal portion (shown in the figure) is provided at an end portion elongated from 5b.
Punched out the metal plate so that
After that, connect the connecting portion 15a to the inside of the opening 1a of the oxygen detecting element.
While rounding into a cylindrical shape with an inner diameter larger than the diameter,
A circle with an inner diameter smaller than the outer diameter of the heater
Rolled into a tubular shape, with the rolled connection 15a and gripping
The bent portion 15e is formed so that the bent portion 15b is on the same axis.
Consists of The heater 6 is firmly gripped by the metal terminal 15 by being fitted into the heater grip 15b,
Further , by inserting the connecting portion 15a into the oxygen detecting element,
It is fixed to the inside of the oxygen sensing element 1 I. Connection part 15a
Is the elastic force that presses the internal electrode layer 2 in the opening 1a in the radial direction.
By exerting a force to settle in the opening 1a, the output of the internal electrode layer 2 can be reliably taken out without being affected by vibration or heat , and the heater can be fixed. It is not necessary to engrave a screw part on the and the assembling work can be easily performed.

In addition, the connecting portion 15a as a fixed portion
And the grip portion 15b are formed by rolling a metal plate into a cylindrical shape.
The oxygen sensor is exposed to external vibration and shock.
Even if it crosses, the connecting portion 15a and the grip portion 15b
Vibration and shock are alleviated by elastic deformation of
Damages the internal electrode layer 2 and the ceramic heater 6.
Without having to go through, it is possible to maintain a state in which the heater 6 holding fixed to the oxygen sensing element 1 in the metal terminal 15. Therefore, the oxygen sensor of the present embodiment is suitable as a vehicle-mounted oxygen sensor that is susceptible to vibration and impact.

The oxygen sensor according to this embodiment is actually
Is the drop of about 1m required by ordinary engine makers?
After performing a drop impact test,
Also, a rod-shaped ceramic heater with an outer diameter of about 2.5 mm and a length of about 60 mm
The data 6 and the internal electrode layer 2 were not damaged at all,
The heater 6 held by the metal terminal 15 is installed in the oxygen detection element 1.
It was fixed and kept in the same condition as before the test.

In this embodiment, the connecting portion 15a of the metal plate 15 is formed by forming a rectangular metal plate into a cylindrical shape, but in addition to this, as shown in FIG. 3, for example.
The metal plate may be formed into a cylindrical shape by forming a rectangular cut, or the metal plate may be formed into a cylindrical shape by forming a wavy cut as shown in FIG. In this case, the metal terminal has a plurality of pressed portions of the internal electrode layer, and for example, a part of the metal terminal is deformed by a force from the outside.
Even if the pressing portion P1 shown in (1) loses its resilience, the metal terminals can be firmly fixed to the internal electrode layer by the resilience of the other pressing portions P2 to P4. The oxygen detection element can be more firmly fixed in the cylindrical shape, and the output from the internal electrode layer can be more reliably taken out.

[Brief description of drawings]

FIG. 1 is a drawing showing a partially broken front surface and a left side surface of an oxygen sensor of this embodiment.

FIG. 2 is a side view of a metal terminal 15 of the present embodiment and a drawing showing a developed state.

FIG. 3 is a diagram showing a side view and a developed state of another example of the shape of the metal terminal.

FIG. 4 is a drawing showing a side view and a developed state of still another example of the shape of the metal terminal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Oxygen detection element, 2 ... Internal electrode layer, 4 ... Output extraction lead wire, 6 ... Heater, 15 ... Metal terminal,

Claims (2)

[Claims] 1. A and the oxygen sensing element of tubular, one end of which is closed with an electrode layer on the inner and outer surfaces, a heater for being inserted into the tubular heating the oxygen sensing element, the oxygen sensing element inner surface And an output lead wire electrically connected to the internal electrode layer of the above , in an oxygen sensor, the output lead wire and the internal electrode layer are electrically connected.
A metal terminal for connecting to the front side of the oxygen detection element
Inside the cylinder, the oxygen is detected by the elastic force of the metal plate.
By pressing the internal electrode layer outward in the radial direction of the element
An oxygen sensor , comprising : a connection part for fixing and a grip part for gripping the heater . 2. A cylindrical oxygen sensing element having one end closed,
For inserting into the cylinder to heat the oxygen sensing element
In an oxygen sensor equipped with a ceramic heater,
For fixing the ceramic heater to the oxygen sensing element
The fixing metal fitting of is made by bending a metal plate into a tubular shape,
In the cylindrical shape of the oxygen detection element, the elastic force of the metal plate
By pressing the inner peripheral surface of the oxygen sensing element radially outward
An oxygen sensor , comprising : a fixed part that is fixed and a grip part that grips the ceramic heater .